1. Field of the Invention
The present invention generally relates to a silver powder and a method for producing the same. More specifically, the invention relates to a silver powder for a conductive paste for use in electronic parts, such as internal electrodes of multilayer capacitors, and conductive patterns of circuit boards, and a method for producing the same.
2. Description of the Prior Art
In order to form electrodes of hybrid ICs, multilayer ceramic capacitors, chip resistors and so forth, cermet type conductive pastes (or conductive pastes of a type to be fired) have been used. A typical cermet type paste includes a silver powder, a vehicle containing ethyl cellulose or acrylic resin dissolved in an organic solvent, a glass frit, an inorganic oxide, an organic solvent, a dispersing agent and so forth as components. The cermet type paste is formed by dipping or printing so as to have a predetermined pattern, and then, fired to form a conductor. As a method for producing such a silver powder for a conductive paste, there is known a wet reduction process for adding a reducing agent to a water reaction system, which contains silver ions, to deposit silver particles by reduction (see, e.g., Japanese Patent Laid-Open No. 8-176620).
However, there are some cases where a silver powder produced by a conventional wet reduction process contains impurities due to entrainment of reacting mother liquor during reduction. Therefore, if a paste containing such a silver powder is used for forming a conductor, there are some cases where the conductor is bulged and/or broken due to volatilization of gas components and so forth during firing.